The present invention is particularly applicable for use in a container of welding wire having a natural “cast” and the invention will be described with particular reference to a natural cast type of welding wire stored as a large wire stack or coils or wire containing convolutions formed into layers of the welding wire which is paid out from the wire stack or coils through the upper portion of the container storing the wire stack or coils. However, the invention has broader applications and may be used with any type of welding wire contained in a wire stack or coils to be fed from the wire stack or coils through the top of the container with or without a tendency to retain a generally straight condition.
Bulk welding wire is commonly packed loosely in large storage containers (e.g., stack of wire in drum or box) or tightly wound on wooden reels. Welding wire that is shipped in large storage containers is often package in a stacked form having a cylindrical inner core. When it is desired to use the wire, a cone assembly is commonly mounted at the top of the container. The cone assembly includes a rotating payout arm extending upwardly from the top of the cone that is provided with an eyelet at its end and a central conduit for guiding the wire to a wire feeder mechanism.
When welding automatically or semi-automatically, it is essential that large amounts of welding wire be continuously directed to the welding operation in a non-twisted, non-distorted non-canted condition so that the welding operation is performed uniformly over long periods of time without manual intervention and/or inspection. It is a tremendously difficult task to be assured that the wire is fed to the welding operation in a non-twisted or low twist condition so that the natural tendency of the wire to seek a preordained natural condition will not be detrimental to smooth and uniform welding.
To accomplish this task, welding wire is produced to have a natural cast, or no-twist or low twist condition. When such wire is wrapped into a wire stack or coils into a large container containing several hundred pounds of the wire for automatic or semi-automatic welding, the natural tendency of the wire makes the wire somewhat live when it is wrapped into an unnatural series of convolutions, distorting the wire from its natural state. Thus, manufacturers produce large containers of welding wire which must be removed from the container without tangling, forming e-scripts and/or introducing unwanted canting into the wire itself.
In automatic and/or semi-automatic welding operations, a tremendous number of robotic welding stations are operable to draw welding wire from a package as a continuous supply of wire to perform successive welding operations. The advent of this mass use of electric welding wire has caused tremendous research and development in improving the packaging for the bulk welding wire. A common package is a drum where looped welding wire is deposited in the drum as a wire stack, or body, of wire having a top surface with an outer cylindrical surface against the drum and an inner cylindrical surface defining a central bore. The central bore is often occupied by a cardboard cylindrical core as shown in Cooper U.S. Pat. No. 5,819,934, which is incorporated herein by reference. It is common practice for the drum to have an upper retainer ring that is used in transportation to stabilize the body of welding wire as it settles. This ring remains on the top of the welding wire to push downward by its weight so the wire can be pulled from the body of wire between the core and the ring. Each loop of wire has one turn of built-in twist so that when it is paid out, the twist introduced by releasing a loop of wire is canceled. Hence the wire is“twist-free” when it reaches the contact tip. The built-in twist causes the wire to spring up from the top of the stack when unrestrained. The weighted ring inhibits or prevents the wire from springing up due to the built-in twist which can result in the wire becoming tangled. Tangles are detrimental to the operation of the package since they cause down time of the robotic welding station. The most common tangle is caused as wire is pulled from the inside of the ring and is referred to as “e-script” because of its shape. E-scripts in the wire can be attributed to several factors such as poor drive roll alignment in the feeder, inconsistent loop diameter, inconsistent fan-out of the loops, settling of the wire during transportation, and abuse in handling the drum of wire. An e-script tangle stops operation of the welder and must be removed. As a result, the tangling of the wire during the paying out of the welding wire results in the welding process having to be stopped, thus resulting in downtime. Such downtime reduces productivity efficiencies and increases production costs. This problem must be solved by manufacturers of welding wire as they sell the welding wire in quantities to be paid out for automatic and semi-automatic welding. This problem is compounded with the trend toward even larger packages with larger stocks of welding wire to thereby reduce the time required for replacement of the supply container at the automatic or semiautomatic welding operation. Consequently, there is an increased demand for a container which is easily adapted to a large capacity and is constructed in a manner such that withdrawing of the welding wire from the container is accomplished smoothly without disturbing the natural flow of the welding wire or twisting the welding wire with adjacent convolutions.
Tangling of the wire can cause interruption of wire flow and drastically interrupt the welding operation. Thus, a large volume, high capacity storage or supply container for welding wire formed in wire stacks or coils must be so constructed that it assures against any catastrophic failure in the feeding of a wire to the welding operation and the container. Further the payout or withdrawing arrangement of the container must be assured that it does not introduce even minor distortions in the free flow of the welding wire to the welding operation. Consequently, there is a substantial demand for a container and withdrawing arrangement for large quantities of welding wire which not only prevents tangling and disruption of the supply of welding wire to the welding operation but also prevents e-script tangles under adverse conditions such as abuse in the handling and poor wire feeder drive roll alignment, together with excellent wire placement consistency and reliable wire-to-tip contact without arc flare.
The welding wire stored in the supply container is commonly in the form of a wire stack or coils having multiple layers of wire convolutions laid from bottom to top, with an inner diameter of the wire stack or coils being substantially smaller than the diameter of the container. Due to the inherent rigidity of the welding wire itself, the convolutions forming the layers are continuously under the influence of a force which tends to widen the diameter of the convolutions. However, as the welding wire is withdrawn from the container, the loosened wire portion tends to spring up and disturb or become entangled with other looped layers or with itself causing premature pop out of the wire loop to the inside bore, causing the top loop of the wire to move under lower wire loops, causing the wire loop to stretch and extend beyond the outside diameter of the wire stack and thereby fall down the outer periphery of the wire stack, and causing an expanded loop diameter of the wire resulting in the wire popping up above the outer periphery of the retaining ring thereby catching the ring. In such cases, it becomes difficult to withdrawn the wire or feed the wire smoothly. In some of the prior containers, the wire is provided with a preselected twist when inserting the wire into the package in order to prevent torsional deformation of the wire which is being withdrawn axially from the non-rotating container. Consequently, the packaged wire of the wire stack or coils tends to spring up with a greater force. As a result, retainer rings or members are placed on the top of the wire stack or coils to hold the wire in the upper layers in place as it is withdrawn, convolution at a time, from the center opening of the wire stack or coils through the top opening of the supply container.
In the past, substantial effort has been devoted to the prevention of the wire springing up which can result in a feeding error from the container. This feeding error is normally prevented by a center tube of cardboard placed in the wire stack or coils cavity so that all convolutions must be withdrawn from around the center tube. In the prior art, the ring itself contacts the inner surface of the container to prevent convolutions from springing above and around the outside of the retainer ring. In the past, the retainer ring generally rests upon the top of the wire stack or coils by gravity. The suspended float ring assembly is placed on top of the wire in the container to assist in keeping the wire from becoming tangled as it is fed out of the container. The suspended float ring assembly commonly includes an annular metal ring that surrounds the inner core and a plurality of flexible fingers or feathers that extend radially outwardly and slightly upwardly of the ring and into contact with the inner surface of the drum. These fingers, constructed of plastic. The float ring is suspended, that is, it rests freely at the top of the coil of wire in the container. Some of the prior rings have had a series of flat spring steel fingers attached to the retainer ring. These fingers tightly ride against the drum to control the outside convolutions of wire. In some instances, a cardboard ring is cut to the desired shape with a slight interference with the drum wall. This ring is held on the top of the wire stack or coils by a weight which travels down the drum as the wire level is reduced.
All of these arrangements present difficulties. Wire can be tangled on the outside of the ring and substantial drag can be imparted to the wire as it is being paid out or withdrawn from the container. As the wire is removed from the container, a part of the wire coil sprang upwardly and become caught between the float ring and the inner core, or wrap around the core, or forms a knot, thus causing a tangle. Also, the wire above the float ring would sometimes wrap around the inner core, particularly as the float ring assembly descended downwardly as the container emptied.
In an effort to address these problems, an improved retainer ring was developed as disclosed in U.S. Pat. No. 5,277,314. The retainer ring or retainer member included a generally flat outer portion with an outer periphery fitting into a set diameter of the inner wall of the container and had a number of projecting lobe portions whereby the outer periphery of the retainer ring contained alternate areas that were closer to and then farther away from the outer wall of the container when the retainer ring was resting on the upper surface or top of the hollow, cylindrical wire stack or coils of welding wire. The retaining ring also had an inner bell mouthed portion defining an innermost wire extraction opening wherein the convolutions of wire are pulled up through the bell mouthed portion which extended upwardly toward the outlet guide in the top cover or “hat” of the container. The convolutions of wire, as they were pulled from the wire stack or coils, move inwardly toward and into the center cavity of the wire stack or coils and then upwardly through the bell mouth portion toward the exit guide in the container hat. The wire extraction opening defined by the upper end of the bell mouthed portion of the retainer ring included a diameter substantially smaller than the selected diameter of the wire stack or coils itself so that the wire must moved move inwardly before it can move upwardly. By using this bell mouthed concept, the inward movement of the convolutions from the wire stack or coils did not have better support against other convolutions and does not have better support drag along the bottom of the retainer ring as the convolutions from the upper layer were moved inwardly and then upwardly to the outlet guide in the cover or hat of the supply container.
Another prior art retaining ring is disclosed in U.S. Pat. No. 5,758,834. The wire control ring is mounted at the upper part of the inner core and provided with finger and an arrangement that prevents the wire from entering into the space between the ring and the core. The wire control ring has an annular metal ring having an inner diameter which is slightly greater than the outer diameter of the drum's inner core, and an outer diameter which permits the unobstructed removal of wire from the drum. A set of three or four fingers or feathers attached to the ring extend outwardly and slightly upwardly into contact with the inner surface of the drum. The width of these fingers is significantly greater than the width of the prior art feathers to insure that the wire is forced against the inner surface of the drum as it is pulled from the drum and removed. The stiffness of the feathers is such that the wire cannot by itself uncoil and exit the drum, but it not so stiff that the resistance to wire movement from the drum adversely affects the wire feeding process. A diverter member prevents wire from inadvertently entering the space between the ring and the drum's inner core.
Although these retaining rings have reduced the incidence of tangling of the welding wire paid out from a container of welding wire, e-scripts still occur during payout of the welding wire. These e-scripts in the wire can result in non-uniformity of a formed weld bead on a workpiece as the twist in the welding wire is fed through a welding gun. The non-uniform weld bead can result substantial downtime of the welding process in order to untangle the welding wire.
Loosely wound wire in a drum typically results in better wire placement during a welding operation; however, such loosely wound wire is more susceptible to tangling. Tightly wound wire on a reel is more resistant to tangling, but is more likely to result in having wire wobble (poor wire placement) during a welding operation. One reason for the higher incidence of tangling for loosely wound wire is that such loosely wound wire is more susceptible to vibration in normal shipping and handling than tightly wound wire on wooden reels. The wire loops of the loosely wound wire tend to move around during normal transportation to warehouse or customers. The moving or shift of the loosely wound wire in a container also occurs from handling abuse in a warehouse and in a factory wherein the drum is tipped to its side and sometimes laid sideways and rolled despite the warning label. Such improper handling tends to shuffle the wire loops and the original order of laying pattern is disturbed. A full drum of wire is typically not entire full but has head room left for the retainer ring. The drums of welding wire are sold with various weight specifications. Wire of various weights and diameters usually share the same fixed size drums. Therefore the drum must be large enough to accommodate the largest weight and smallest diameter (which has the largest volume) wire. As a result, the head rood in containers of wire varies from product type to product type. During shipping and handling of the container of wire, there is vibration which causes the stack of wire coils to act like a spring. A steel bar positioned in the top of the container and held down by a rubber band to the bottom of the drum is often used to restrain bouncing of the wire stack during shipping and handling. Compressible foam is also used to fill the space between the top of the stack to the drum lid. The use of a steel bar and/or foam remedies are not 100% effective, thus stack bouncing still occurs during transportation and handling. As a result, there is noticeable settling of the wire stack (i.e. up to 5 inches) depending on wire diameter, loop and drum diameter, stack volume, and transportation distance and road condition. Settling of the wire in the container changes the original laying pattern thus resulting in the tangling of the wire as it is paid out of the container. The settling typically has a corkscrew form. Since the wire loops fan out in the same direction from the bottom of the drum all the way to the top, the wire has a natural “slope” for wire loops to corkscrew downward.
One prior art process for filling a storage container with welding wire includes the drawing of the welding wire from a welding wire manufacturing process and feeding the welding wire typically over a series of dancer rollers and to pull the welding wire by a capstan positioned adjacent the storage container. From the capstan, the welding wire is fed into a rotatable laying head, which is generally a cylindrical tube having an opening at the bottom or along the cylinder adjacent to the bottom. The wire extends through the tube and out the opening, whereupon it is placed into the storage container.
The laying head typically extends into the storage container and rotates about an axis generally parallel to the axis of the storage container. The wire being fed into the laying head by the capstan is fed at a rotational velocity different than the rotational velocity of the laying head. The ratio between the rotational velocity of the laying head and the rotational velocity of the capstan determines the loop size diameter of the wire within the storage container. As the wire is laid within the storage container, the weight thereof causes the storage container to gradually move downward. As the storage container moves downward, the laying head continues to rotate, thus filling the storage container to its capacity. The storage container is incrementally rotated in one direction by a fraction of one revolution for each loop of wire being placed within the storage container. This rotation of the storage container causes a tangential portion of the welding wire loop to touch a portion of the inside diameter of the storage container, while the opposite side of the loop is spaced a distance from the side of the storage container. This is accomplished by moving the laying head off the centerline of the storage container by one-half the distance between the loop diameter and the diameter of the storage container.
A typical prior art method of packing a storage container with a welding wire is illustrated in FIG. 1. This method of packing storage containers with welding wire has been somewhat effective in withdrawing welding wire from the storage container during the welding process. However, as illustrated in FIGS. 2 and 3, this packing process can result in a loose density packing of the welding wire within the storage container. Depending on the edge diameter used relative to the storage container, the welding wire has a higher density along the edge portion of the storage container versus the inside diameter of the wire stack itself adjacent the wire stack or coils cavity. This difference in density is caused since more wire is placed along the edge portions of the storage container than is placed along the wire stack or coils cavity. While the net effect results in welding wire being able to be pulled from the storage container without substantial problems with tangles, the low density packing can result in increased tangling of the wire resulting in increased interruptions in the welding process. There is consequently greater downtime for the welding operation, and greater labor costs, since replacement of the supply storage container at the welding operation and manual intervention in the welding operation is necessary. In addition, the loose packing of the wire can result in the wire shifting during movement or shipment of the storage container, which shifting of the welding wire can result in disorder of the wire loops which can result in tangling of the welding wire in the storage container. These wire shifting can result in an outside ring tangle where wire loop pops up in the clearance between drum inner diameter and outside periphery of the retainer ring, an e-script tangle wherein the excess wire length between the inner diameter of the retainer ring and exit hole of the hat forms a knot, wire loop expansion beyond the periphery of the wire stack resulting in the wire loops cascading down the clearance between the outside periphery of wire stack and drum inner diameter, and/or birdnests from multiple loops of wire being pulled out at the same time. As a result, such wire shifting can result in payout stoppage of the welding wire from the storage container, which in turn results in the welding operation having to terminate to correct the payout problem.
One prior art packing arrangement is set forth in Assignee's U.S. Pat. No. 6,260,781. In this patent, a method for densely packing welding wire in a storage container is disclosed. The packing involves the use of an indexing apparatus which allows the storage container and rotatable head to be moved relative to the other in sequential steps during packing of the wire within the storage container. The indexer causes a rotatable laying head to place wire in the storage container from a different position within the storage container, thereby allowing for a more dense packing of the welding wire within the storage container. In addition to using the indexer, the loop diameter of the wire within the storage container can be varied, thus resulting in the production of striated layers of welding wire within the storage container, each layer having a maximum density at a different radial position within the storage container than the adjacent layer. In essence, the indexing step and/or the changing of loop diameter helps to ensure that a storage container of welding wire is more densely packed than previous packing arrangements, thus enabling more welding wire to be placed within the same volume storage container. Although the novel wrapping arrangement disclosed in the '781 patent increases the volume of wire which can be packed into a storage container, the packing arrangement is still not immune to problems of the welding wire shifting during the transport and shipment of the storage container of welding wire from one location to the next. This shifting of the welding wire within the storage container increases the incidence of bird nests forming during the payout of the welding wire from the storage container.
In view of the present state of the prior art for the packaging of welding wire in storage containers, there remains a need for a packaging process which allows for the uninterrupted payout of the welding wire from the storage container, and which packaging arrangement reduces the tendency of the welding wire to shift within the storage container during shipment of the storage container which shifting can result in undesired tangles in the welding wire during pay out from the storage container.